This is a common teaching of the Church. Pope Benedict XVI made a speech where he said, God established in His way and will that all the graces which Christ, the unique redeemer of mankind, obtained for us in His Sacrifice, will be administered by the hands of His holy mother.
According to God's will, Mary is the recipient of these graces first before they are channeled and distributed to the rest of humanity because she is the mother of the Redeemer. This was also a teaching of theologians and Popes in the previous centuries. Its order is according to the way of our salvation, for which God has chosen Mary to be the first, and through her, she gave the world the greatest grace, Jesus Christ.
The humanity of Christ came through Our Lady in Bethlehem on the first Christmas. From this, she was also there at the foot of the cross, as she consciously offered her son for the salvation of the world. As a mother, she renounced her rights, and this is a unique participation in the drama of salvation.
Therefore, God established this way so that we receive all graces through the hands of Our Lady. This is the mediatrix; Mary only intermediates; she is not the fountain of grace because she did not gain grace. Because all graces were entirely obtained through the sacrifice of Christ.
Since she was present in the role of salvation, therefore, she also has the right, received from God, to distribute the graces. Similarly, the Church is also a channel of grace, which she distributes to us through the sacraments. As Mary is the mother of the Church.
Dear visitors of Gloria Dei and all who have already written or who will write a personal message to me. I am grateful for your attention, your kindness, for your spiritual support and especially for your sacrifices and prayers for me. God may reward you!